R函数MergePalette未按预期抛出自定义错误的修复方案

Let's break down why your current code isn't working as expected: when you call MergePalette("Teej"), R throws its default "argument missing" error before your custom error message ever gets triggered. That's because the name2 parameter doesn't have a default value—R requires it to be provided, so it stops execution immediately instead of reaching your is.null(name2) check.

Here's the simple fix: add a default value of NULL to the name2 parameter. This lets R accept the function call even when only one argument is passed, and then your error handling logic can kick in.

Modified Code #

MergePalette <- function(name, name2 = NULL){
  pal <- RanglaPunjab(name)
  if (is.null(name2)){
    stop("Enter 2 valid palettes. Run ListPalette() for list of palettes.")
  }
  pal2 <- RanglaPunjab(name2)
  new_pal <- unique(c(pal,pal2))
  new_pal
}

How It Works Now #

• If you call MergePalette("Teej"), name2 will default to NULL, triggering your custom error message instead of R's generic one.
• When you pass two valid palette names (e.g., MergePalette("Teej", "Lohri")), the function will proceed to merge the two palettes as intended.

Optional Extra Check (For Robustness) #

If you want to make sure the first parameter isn't missing either, you could add a similar check for name:

MergePalette <- function(name = NULL, name2 = NULL){
  if (is.null(name) || is.null(name2)){
    stop("Enter 2 valid palettes. Run ListPalette() for list of palettes.")
  }
  pal <- RanglaPunjab(name)
  pal2 <- RanglaPunjab(name2)
  new_pal <- unique(c(pal,pal2))
  new_pal
}

This way, the function will catch cases where either parameter is missing and show your custom message.

内容的提问来源于stack exchange，提问作者Artie Ladie